1. Cook the chicken breast on a pan over medium heat until fully cooked, about 7-8 minutes per side.
2. While the chicken is cooking, slice the tomatoes and toast the bread if desired.
3. Once the chicken is done, let it rest for a few minutes before slicing it into thin strips.
4. Fry the egg to your liking.
5. Assemble the sandwich by layering the chicken, tomato slices, and egg on one slice of bread. Top with the second slice of bread.